To refinish or repair a finish on vehicle, such as a basecoat/clearcoat finish on automobile or truck bodies, different fast-drying coating compositions have been developed. A number of pigmented and clear air-dry acrylic lacquers have been used in the past to repair basecoat/clearcoat finishes, but none meet the rapid drying times that are desired, while also meeting today's performance requirements, such as excellent stone-chip resistance, humidity resistance, intercoat adhesion, and appearance.
A key concern to a refinish customer which is typically the vehicle owner is that the coating in use has excellent durability and weatherability and an attractive aesthetic appearance.
Another key concern of the automobile and truck refinish industry is productivity, i.e., the ability to complete an entire refinish operation in the least amount of time. To accomplish a high level of productivity, any coatings applied need to have the ability to dry at ambient or slightly elevated temperature conditions in a relatively short period of time. The term “dry” means that the resulting finish is physically dry to the touch in a relatively short period of time to minimize dirt pick-up, and, in the case of the basecoat, to allow for the application of the subsequent clear coat.
It is also desirable to have quick drying basecoats for additional reasons. If the applied basecoat composition layer has not dried sufficiently before the clearcoat composition is applied, then the application of the clearcoat will disturb the basecoat layer and the appearance of the basecoat will be adversely affected. For basecoats containing special effect pigments, e.g., flake pigments such as metallic and pearlescent flakes, the metallic flake control and metallic appearance (or downflop) of these basecoats will suffer due to disturbance of the flake pigment by intermixing of the coating layers at their interface. “Downflop” refers to a phenomenon associate with metallic effect coatings wherein the color varies with the angle of view to provide a three dimensional metallic effect on the surface of the vehicle.
Cost and volatile organic solvent content are further concerns in formulating automotive refinish coating compositions. For example, cellulose acetate butyrate (CAB) resins have been used to shorten the dry to handle time and as rheology control additives to enhance metallic flake control and other properties in refinish basecoats, but coating compositions containing these CAB material require an undesirable high amount of organic solvent. In addition, these CAB materials are relatively expensive and require added steps in the coatings manufacturing process. The CAB materials are also specialty products that are not widely manufactured.
It would be advantageous, therefore, to have a lacquer coating composition, especially a refinish basecoat lacquer, having a short tack-free drying time at ambient temperature conditions, good metallic flake control and appearance, that is less expensive, that has a reduced amount of regulated emissions, and has the ability to form a finish with excellent chip and humidity resistance and adhesion. The novel composition of this invention have the unique combination of properties desired.